Study of gamma-ray bursts afterglow surprises scientists

April 30, 2014

Measurements of polarized light in the afterglow of GRB 120308A by the Liverpool Telescope and its RINGO2 instrument indicate the presence of a large-scale stable magnetic field linked with a young black hole, as shown in this illustration. Credit: NASA's Goddard Space Flight Center/S. Wiessinger

Research from an international team of scientists led by the University of Leicester has discovered for the first time that one of the most powerful events in our universe – Gamma-Ray Bursts (GRB) – behave differently than previously thought.

The study, published in the prestigious scientific journal Nature, uses evidence from observation of a GRB to rule out most of the existing theoretical predictions concerning the afterglow of the explosions.

For Dr Klaas Wiersema, of the University of Leicester's Department of Physics and Astronomy, it was handy that he was up in the middle of the night tending to his three-year-old son which is when he got the alert that a GRB had occurred.

He said: "When a suitable GRB is detected by a satellite, I get a text message on my phone, and then I have to very quickly tell the observatory in Chile exactly which observations I want them to take, and how.

"This is usually a rather stressed and frantic few hours of working, as fast as possible, on my laptop throughout our night-time – and I remember very well that my son, who was three at the time, was up a lot that night too, so I kept on running back and forth between my laptop, my phone to call the observatory in Chile, and my son's cot!"

The effort was worth it- and has led to scientific findings that will change theoretical understandings of the afterglows of GRBs.

Dr Wiersema explains: "About once per day, a short, very bright flash of gamma-rays (the most energetic form of light) is detected by satellites. These flashes are called gamma-ray bursts (GRBs), and take place in galaxies far away, when a massive star collapses at the end of its life.

"These GRBs are followed by a so-called "afterglow", slowly fading emission that can be seen at all wavelengths (including visible light), for a few days to weeks. We know that the afterglow emission is formed by a shockwave, moving at very high velocities, in which electrons are being accelerated to tremendous energies. These fast moving electrons then produce the afterglow light that we detect.

When a massive star dies it explodes as a supernova. The core of the star collapses into a black hole, and in care cases a jet is formed along the rotation axis of the newly formed black hole. Processes in this jet emits gamma radiation, which we observe as a so-called gamma-ray burst. Typically gamma-ray bursts last a few minutes. When the jet hits material surrounding the dying star an afterglow is formed. New observations of the degree of polarization of the afterglow light has shown that the afterglow behaves differently than expected Credit: NASA

"However, how this acceleration process actually works is very hard to study on Earth in laboratories, or using computer simulations. What we do, is study the polarised light of the afterglow using large optical telescopes, and special filters, that work much like the filters in Polaroid sunglasses."

So what is polarised light? Dr Wiersema says it is important to remember that light is a wave – when light is linearly polarised, it means that the wave vibrations lie in a plane; and when light is circularly polarised, it means that that this plane rotates on the sky.

He added: "Different theories for electron acceleration and light emission within the afterglow all predict different levels of linear polarisation, but theories all agreed that there should be no circular polarisation in visible light. This is where we come in: we decided to test this by carefully measuring both the linear and circular polarisation of one afterglow, of GRB 121024A, detected by the Swift satellite.

"Using the Very Large Telescope (VLT) in Chile, we measured both the linear and circular polarisation of an afterglow with high accuracy. Much to our surprise we clearly detected circular polarisation, while theories predicted we should not see any at all. We believe that the most likely explanation is that the exact way in which electrons are accelerated within the afterglow shockwave is different from what we always thought. It is a very nice example of observations ruling out most of the existing theoretical predictions – exactly why observes like me are in this game!

Gamma-ray burst 121024A, as seen on the day of burst by ESO's Very Large Telescope (VLT) in Chile. Only a week later the source had faded completely. Credit: Dr Klaas Wiersema, University of Leicester, UK and Dr Peter Curran, ICRAR.

"We are the first team to realise the importance of trying these technically difficult circular polarisation measurements at visible wavelengths – most people simply assumed it wouldn't be worthwhile doing as theory predicted levels too low to be detectable. The detection of far stronger circular polarisation than expected makes it a particularly surprising result.

"We believe that this detection means that most of the current theories of how electrons get accelerated in afterglows need re-examining."

Dr Wiersema said the research was also important because taking these high precision measurements of a rapidly fading afterglow is very difficult from a technical point of view. The research represents a great technological achievement, one the team would love to repeat for more sources.

"Extreme shocks like the ones in GRB afterglows are great natural laboratories to push our understanding of physics beyond the ranges that can be explored in laboratories," said Dr Wiersema.

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Pejico

Keep in mind, the wrong theories related to this are all closely related to all the other wrong theories in cosmology.

@ Returnering-Skippy, truce temporary okayeei? What are these wrong theories explain to me? And what are the other wrong theories that aren't here but somewhere else? It would help ol Ira-Skippy if you peoples would be more not so vague, eh? That Really-Skippy make a lot of peoples mad with him because he wouldn't tell peoples what he thought was wrong in the cosmic microwave gravity waves thing.

Thanks for you if you can explain to me but I will be mad with you if you tell me like the Really-Skippy that I should know enough to know what you are talking about, eh?

P. S. @ to you Returnering-Skippy. The reason I ask for the explaining of it is not so I can call you stupid or the couyon. I need to know what to put into the google to find out if what you say is right or if what the peoples studying the gamma bursting are right, okayeei?

Since relativity, pretty much everything in science has been re-defined in terms of the assumption of a constant speed of light, and as such pretty much everything in science has been redefined in terms of properties of light. So, if properties of light predicted by a theory are wrong, then the basis of that theory is also wrong, and presumably all other theories based on that theory are in some way wrong.

Since relativity, pretty much everything in science has been re-defined in terms of the assumption of a constant speed of light, and as such pretty much everything in science has been redefined in terms of properties of light. So, if properties of light predicted by a theory are wrong, then the basis of that theory is also wrong, and presumably all other theories based on that theory are in some way wrong.

@ Returnering-Skippy so you are saying that the peoples looking at gamma bursts are not measuring the light at the right speed? Is that what they did to get wrong? So how do we know what they used to measure it with? Maybe they used the right thing to measure the gamma burst light speed. Or better than that maybe you would explain to me how those scientist-Skippys go about measuring the light, what they use for that.

@ Returnering-Skippy so you are saying that the peoples looking at gamma bursts are not measuring the light at the right speed? Is that what they did to get wrong? So how do we know what they used to measure it with? Maybe they used the right thing to measure the gamma burst light speed. Or better than that maybe you would explain to me how those scientist-Skippys go about measuring the light, what they use for that.

forget it. You seem incapable of comprehending basic English grammar and usage, so I don't feel the need to explain myself, nor do I see any point in doing so. You'll just misunderstand or misrepresent anyway.

forget it. You seem incapable of comprehending basic English grammar and usage, so I don't feel the need to explain myself, nor do I see any point in doing so. You'll just misunderstand or misrepresent anyway.

Does that mean you call off the truce? That makes you look look like that Really-Skippy couyon who wants to tell everybody they got it wrong but thinks they are to stupid to understand if he explain it so he doesn't explain because it waste his time.

Look you, I might not know all the fancy science words and ideas. But ol Ira is not the stupid Skippy you think he is non. I can understand a lot things that I can't say real well me. I went to the community college to be the engineer man on the tow it / push it boat me. Bet something you never did guess, ol Ira is the Expert Class chess player. This year I will be the Candidate Master and if I get my norms will be the National Master rated chess player USCF and 2250 FIDE, can you do that?.

You just misrepresented Really-Skippy, because Really -Skippy merely advised everyone to read and find the obvious flaws in that mainstream 'paper' on the CMB, that's all. Even the mainstream peers immediately pointed to the same flaws I saw. So why should anyone get angry with Really-Skippy for encouraging everyone here to do their own due diligence and find the same obvious flaws for themselves?

And I have stopped 'explaining' anything online because I am publishing a complete and consistent ToE book. That's all.

So poor poor Uncle Ira BOT troll is not only useless but totally ignorable as well, and no-one anywhere will be any the worse for ignoring your idiotic internet trolling and misrepresenting. So Returners was right to say that you wouldn't understand (because you are a BOT) and would only misrepresent (because Uncle Ira BOT operator is a troll). :)

Hey Really-Skippy where you at Neg? Did they give you the boot again over at your other place? We not see much lately no. For all those peoples being right, they sure aren't to good at it. Tell me some truth Cher, I'm hard to ignore, eh?

Laissez les bons temps rouler Really-Skippy I think I go check in at that other place to see if you been making them the misere again.

You just proved again that everyone is right to ignore your trollish idiocy.

I am still posting over there, you idiot trollbot. And the only ones causing the problems are the same old 'usual suspect' troll-mods' who don't know when to quit being idiotic troll-mods abusing their position.

Just like you, they are insensible as to still think no-one is watching.

You would be perma-banned immediately if you just posted your troll-BOT drivel over there. The fact that you are not permabanned from here says that you are one of the site's own 'moderators' OR one of its protected trolls. Either way, your continuing presence here is an embarrassment to the site and drags down its reputation as a serious science news/discussion site/forum.

Good luck with your nasty and worse than useless life/internet interaction choices so far, idiot trollbot, whoever you are! You'll need it when your Krazy Karma comes back to bite you on the bum, shitehead. Lol.

@ Really-Skippy, apology accepted. I'm glad you are going to do better now, we'll all be watching just to make sure.

Laissez les bons temps rouler Really-Skippy.

Oh yeah, I almost forgot this to say:

Just like you, they are insensible as to still think no-one is watching.

Why would ol Ira-Skippy think nobody is watching? I get the fan mails almost every day. Most it has to do with Really-Skippy and some of the other Skippys. That means I know somebody is watching. You must be watching Cher because that is how ol Ira knew to write you this, eh?

@ Really-Skippy, what you tell them peoples that ol Ira-Skippy was coming by to sit on the gallery for the while? What you get from telling people they shouldn't have anything to do with me? Not a thing to worry about non, ol Ira knows a few tricks from experiencing this before, it will just take me a little of time to see if you are truth telling about not getting the boot over there again.

Laissez les bons temps rouler Really-Skippy I'll let you know what I find out about if you are truth telling on that one. I have the doubts me about that, because so far your record at the track is not Really-Skippy-Good.

If he was playing poker whilst dealing with the GRB would that be cool? How about watching a movie? Hey, kids are a hobby too. Reject the preaching of the human factory farmers. Having kids is no service to anyone. We don't need more kids. It's for personal vanity and it is not helpful. It's a hobby. It isn't professional to indulge your hobby whilst working.

New observations of the degree of polarization of the afterglow light has shown that the afterglow behaves differently than expected.

Is this referring to the circularly polarized luminescence, then?

Aren't the incident electrons tracing out the path of a helix?

Would the E- and B-fields in the jet be rotating to a degree proportional to the rotation of the collapsing star?

From the abstract:"…We show that the circular polarization is intrinsic to the afterglow and unlikely to be produced by dust scattering or plasma propagation effects. A possible explanation is to invoke anisotropic (rather than the commonly assumed isotropic) electron pitch-angle distributions, and we suggest that new models are required to produce the complex microphysics of realistic shocks in relativistic jets."

and we suggest that new models are required to produce the complex microphysics of realistic shocks in relativistic jets."

So they need to improve their understanding double layers (DL), enter the physics developed by Alfven and Pratt, et al. The helical pattern is ubiquitous with Birkeland currents. The DL is ubiquitous to Birkeland currents as well, and clearly capable of generating the gamma rays. You can find out more here, a second edition that reexamine predictions made 20 years ago in the first edition;http://www.spring...4-7818-8

Try your local library, it'll be cheaper.

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